Recovery of helium



March 17, 1925. 1,530,461

A. H. GRAHAM RECOVERY OF HELIUM' Filed Sept. 25, 1922 2 Sheets-Sheet l vMarch 17, 1925. 1,530,461

A. H. GRAHAM- RECOVERY OF HELIUM Filed Sept. 25, 1922. 2 Sheets-Sheet 2XQN mill km N K3 x Y i atented Mar. 17, 1925. UNITED STATES PATENTOFFICE.

ARTHUR H. GRAHAM, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO GAS EQUIP-MENT ENGINEERING CORPORATION, OF PHILADELPHIA, PENNSYLVANIA, A GOR-IPORATION OF DELAWARE.

RECOVERY OF HELIUM.

Application filed September 25, 1922. Serial No. 590,554.

To all whom it may conccwt: The refrigerating apparatus generally in- 65Be it known that I, ARTHUR H. GRAHAM, dicated at 4, is a means forproducing the a citizen of the United States, residing at region ofrefrigeration at 1 by the use of Philadelphia, in the county ofPhiladelphia air or nitrogen liquefied at' high pressure 5 and State ofPennsylvania, have invented 'which reaches the expansion valve 5 by waya new and useful Improvement in the Reof the path 6, and then traversesthe coil covery of Helium, of which the following 7 and leaves by thepath 8. This region is a specification. of refrigeration includes a heatexchanger,

The principal object of the present ingenerally lndlcated at 10. Theheat exin vention is to facilitate the recovery of hechanger shown maybe described as follium from natural gas and to simplify and lows: 11 isa shell subdivided by tube sheets, improve the process of recovery.Other obarranged in pairs with space 13 between jects of the inventionwill appear from the the plates of each pair, into high and lowfollowing description of the invention, and pressure chambers arrangedin alternathe invention will be claimed at the end tion. The chambers a,a 0, and are nection with the accompanying drawings Z), 6 b and b arelow pressure chamforming part hereof and in whichbars. The gas passes bytubes 14 connected Figure 1 is a view illustrating diagramwith thespaces 13 between the tube sheets 2n matically and schematically oneform of apand extending across the chambers, and the paratus for thepractice of the invention, gas finally reaches the separator. l by theand connection 15. There are tubes 16 which Fig. 2 is a similar viewillustrating a connect the low pressure chambers and there modification.are what may be called jump pipes 17 which -13 The practice of themethod of the invenconnect the lower portions of each of the tion may bebriefly said to include three high pressure chambers with the next highprincipal steps or operations: First, total pressure chamber in theseries. These jump liquefaction of substantially all of the conplpes 17are also in communication with the stituents of the gas other thanhelium; secspaces 13 between the pairs of tube sheets 0nd, removal ofthe uncondensed helium at by way of the connections 18. The inlets a lowtemperature; and third, vaporization of expanders 19 are connected withthe of the liquid in stages or fractionally at high pressure chambers asby 20, and the approximately the pressure under which it outlets of theexpanders are connected as was condensed, thereby similarly effecting by21 with the low pressure chambers. 22 condensation of nearly alikequantity of may be said to be an extension of the heat incoming gas sothat a material economy exchanger 10, and is itself a heat exchanger iseffected and the recovery of helium or cooler and the parts of it whichcorincreased. respond with the heat exchanger 10 are The invention willbe further described marked with the same numerals, having in connectionwith the accompanying drawadded thereto the exponent a. 23 isacoui ingshaving particular reference to Fig. 1 pressor which is driven by powerfrom a in which there is illustrated apparatus of suitable source ofpower applied as at 24:, which the heat exchanger shown at the botandalso by such power as is available from tom of the sheet is in sectionalelevation and the expanders 19 with which it is geared in which theapparatus shown at the upper as by gearing 25. part of the sheet isprincipally in sectional Natural gas entering at 26 is subjected plan,the view being thus distorted for the to the action of the compressor 23and then sake of clearness in explanation. The seppasses as by 27through cooler 28, through arator 1 is a part of a region ofrefrigerapipe 29, through cooler or heat exchanger tion at which heliumwill not liquefy and 22, and through tubes of heat exchanger 10 fromwhich it is withdrawn at low temto separator 1, from which the liquidminus 5 perature by way of the outlet 2. In this substantially all ofthe helium passes by region substantially all of the other conpipe 30back through the heat exchanger stituents of the natural gas willliquefy. 10 in a manner that will be presently dehereof, but will befirst described in conhigh pressure chambers and the chambers 70scribed, the products of vaporization or gas escaping at 31.

From the foregoing it will be evident to those skilled in the art that astream of natural gas under pressure in traversing the tubes of thecooler 22 exchanges its heat, or some of it, with the medium surroundingthose tubes, and such vapor as may condense is withdrawn by way of theconnections 18, and generally speaking, the same action takes place inthe tubes of the heat exchanger 10, so that finally the gas at a verylow temperature and under pressure is subjected to the described actionof the separator 1, and the helium, or substantially all of the helium,is led off at 2 at a low temperature. The liquid returning by enters thehigh pressure chamber a and is distributed in intimate contact with thetubes 14 therein, and a part of it evaporates, and the whole masstogether with liquid condensed out of the natural gas between the pairsof tube sheets and escaping therefrom by the connection 18 is passed bythe jump pipe 17 to the high pressure chamber a In the high pressurechamber a a portion of the liquid is vaporized and the resulting gas ispassed through an expander 19 and back to the low pressure chamber 6where there is an exchange of sensible heat from the incoming gas, andthen passes by 16 to the low pressure chamber 6 and the remainingportion of the liquid passes by jump pipe 17 to high pressure chamber aand the described operation is repeated through the high and lowpressure chambers and apparatus shown in the drawing progressively fromthe right towards the left. The number of repetitions is not ma terialand may be increased or diminished and a description of one suchoperation is believed to be suflicient.

The chambers in the apparatus 22 at the left in the drawing are cooledby returning low pressure gas and by the liquid which has condensed fromthe incoming natural gas and which is withdrawn from spaces 13 by theconnection 32.

From the foregoing description it appears that, generally stated, thereis established a region of refrigeration at which helium will notliquefy and from which it iswithdrawn at low temperature and at whichsubstantially all the other constituents of the natural gas willliquefy. I do not desire to define the exact extent of that regionbecause it may vary in different cases, but what I mean in a general wayis the region included by the apparatus 10. Through that region ofrefrigeration I lead a supply of natural gas under pressure and I effectheat exchange between that incoming supply of gas and the outgoing gasand its liquid constituents, and this I do by vaporizing the liquidconstituents of the outgoing gas along sulting from the vaporization iswithdrawn,

expanded and cooled and the sensible heat of the expanded gases is usedat low pressure, and this operation is repeated.

I believe that the described vaporization of the liquid in such a waythat it will absorb the larger part of the heat of condensation of theincoming gas is new, and I also believe that it is new to provide theconnections indicated at 18 and the jump pipes indicated at 17, so thatit is an important feature of the invention that liquid from theincoming gas is taken from high pressure chambers and put as liquid intoother high pressure chambers, by-passing the low pressure chambers, incontra-distinction to the customary practice in which such liquid waspassed from a high pressure chamber directly into a low pressurechamber.

It may be said that the final refrigeration or liquefaction of thecondensable gases in the vessel 1, is effected by expanding liquidnitrogen or air, and that the liquefaction of the other fractions of theincoming gas is accomplished according to equilibrium by fractionalvaporization of the outgoing liquid in suitable contact with theincoming supply and at pressures and temperatures substantially the sameat like points of condensation and vaporization, and it may also be saidthat by withdrawing the condensate from the incoming supply and addingit in stages to the outgoing gas supercooling of the condensate isavoided.

As shown in Figure 1, this is accomplished by providing high pressurechambers a.

a a and a", in the return circulation, but in Fig. 2 these chambers areomitted as are also the expanders 19. However in certain essentials theoperation is the same. In Fig. 2thc parts which correspond to the partsshown in Fig. l. are marked with the same numerals with the addition ofthe exponent x. and in Fig. 2. 10" is a region of refrigerationconsisting of a countercurrent interchanger wherein 11 is a tube orseries of tubes arranged sons to be surrounded by a larger tube 14 withspace 13* between the tubes which space 13* communicates with thechambers 35 located at one end of tubes 14". Pipes 18 connect chambers35 with tubes 11". 21 is a chamber enclosing the greater portion oftubes 14*.

Gas which has been previously treated for the removal of water vaporsand carbon dioxide enters at 26 where it is compressed by compressor 23*and enters water cooler. 28* by pipe 27*. Pipe 29* con ducts cooled gasto tubes 14* where it travels through the spaces 13* to pipe 15* whichleads to the separator 1*. Here the gas comes in contact with a coil 7*which is cooled by liquid air or liquid nitrogen supplied byrefrigeration plant 49. Practical- 1y all of the gas except the helium,is liquetied at this point and the helium, is removed through pipe 2*.The liquefied gas is returned to 10* through pipe 16* where there is anexchange of sensible heat from the incoming gas and continues throughtubes 11* until a region is reached wherein the temperature causesevaporation according to the vapor pressures of the gas. At these pointsfractional condensation will take place within the spaces 13*, therebyutilizing the latent heat of evaporation of the gas in tubes 11* incondensing approximate ly a like amount of gasin spaces 13* untilequilibrium between the amount of vapor and gas present in spaces 13*and in tubes 11* has been reached. The liquids so condensed in spaces13* will collect in chambers 35 and will be removed by pipes 18* totubes 11* where these liquids will exchange their sensible heat and heatof va porization with the gasin spaces 13* thereby continuing theprocess of cooling and condensing the gas in spaces 13*. The gas willtravel through the series-of tubes 11* until it reaches approximatelythe temperature of the incoming gas. It will leave the region 10* bypipe 31* at substantially its original pressure. By this process, aftersuitable temperatures have been reached and the fractional condensationof the gas is taking place throughout the system and the system is insuch condition that practically the only constituent of the liquid inthebotom of separating chamber 1* is nitrogen, compressor 37 may be shutdown, valves 9* and 5* closed, valves 22* and 32 opened and part oftheliquid nitrogen from the bottom of separating chamber 1* can beremoved by pipe 19* to throttle valve 5, where it will be expanded intocoil 7* and will leave coil 7* through chamber 8*, passing by pipe 20*to nitrogen chamber 21* where it will exchange its sensible heat withthat of the gas in spaces 13*, and will finally lead outof the system atoutlet 30*, thereby increasing the heating value of the gas by removingsome of the nitrogen.

\Vithout limiting the invention I may say that pressure ranging from 19to 25 atmospheres, more or less, will beneficially affect the percentageof helium recovered. In the auxiliary cycle generally referred to in thedrawings at 4 and 4*, air or nitrogen are equivalents and when nitrogenis referred to in the claims the intentlon is to include air. It may besaid that the temperature of the liquid condensate from the liquefy,

' cycle and that the natural gas is lowered by the auxiliary aseoushelium is withdrawn at substantially the pressure and temperature of itsminimum solubility in the liquid present.

From the foregoing description it is evident that I have provided amethod of separation of helium from the liquefied natural gas whicheliminates the use of any of the usual forms of fractionating orrectifying columns.employing the use of plates with bubble caps or likedevices and providing a definite reflux of the components of highestvapor pressures and that my method of operation as described, is inemphatic con:

tra-distinctio-n tomethods employing usual.

fractioning or rectifying columns or both.

'It will be obvious to those skilled in the art to which the inventionrelates that modifications may be made in details of construction andarrangement and procedure without departing from the spirit of theinvention which is not limited as to those matters or otherwise than asthe prior art and the appended claims may require.

I claim;

1. In the recovery of helium from natural gas the improvement in thestep of frac-' tionally condensing constituents other than helium of theincoming natural gas by heat exchan e with the outgoing liquidcondensate w ich consists in vaporizing the re; spective constituents ofthe condensate under temperature and pressure conditions substantiallylike the temperature and pressure conditions under which they werecondensed, substantially as described.

2. In the recovery of helium from natural gas the improvement in thestep of fractionally'condensing constituents of the incoming natural gasby heat exchange with the outgoing liquid condensate which consists invaporizing the respective constituents of the condensate underconditions substantially like the conditions under which they werefcondensed, and permitting the outgoing tially as described.

1. The process of recovering helium from natural gas which consists insupplying and expanding a suitable liquid to'establish a region ofrefrigeration at which helium will not liquefy and from which it iswithdrawn at low temperature and at which substantially all otherconstituents of the gas will leading and in steps condensing a stream ofnatural gas containing helium under pressure through sald region, andeffecting heat exchange between said streamv of gas and liquidconstituents by vaporizing the latter in stages at approximately thepressure under which they were condensed, thereby effecting condensationof nearly a like quantityof incoming gas.

5. In the art of recovering helium from natural gas the improved stepwhich consists in effecting heat exchange between the natural gas underpressure and the outgoing liquid by evaporating the liquid at highpressure in alternate stages, and expanding and cooling the gasevaporated from the liquid and applying its sensible heat at intermediate stages.

6. In the recovery of helium from natural gas the improved step whichconsists in effecting heat exchange between the incoming gas and theoutgoing liquid condensate by vaporizing the condensate in stages undertemperature and pressure conditions substantially like the temperatureand pressure conditions under which it was condensed.

7. In the process for the recovery of helium from natural gas in whichthe constituents other than helium are condensed and the helium drawnofi in a region of refrigeration, the improvement which consists inproducing the temperature of refrigeration in said region by anauxiliary cycle of liquid nitrogen and in vaporizing the re turningliquid in heat exchange relation with the incoming sup ly of gas attemperatures and pressures substantially identical with the temperaturesand pressures at which they were condensed.

8. In the process for the recovery of helium from natural gas in whichthe constituents other than helium are condensed and the helium drawnoff in a region of refrigeration, the improvement which con sists-inproducing the temperature of refri eration in said region by anauxiliary cyc e of liquid nitrogen and in fractionally vapor-- izing thereturning liquid in heat exchange relation with the incoming supply ofgas at temperatures and pressures substantally identical with thetemperatures and pressures at which they were condensed.

ARTHUR H. GRAHAM,

